Unit 2The Basic Principle of EngineText A Classification and Main Components of Engine游海龙The internal combustion engine is an engine in which the combustion of fuel occurs with oxygen(usually air) in a combustion chamber, as shown in Fig.2.1.1 87692 3 45Fig.2.1 Internal Combustion Engine1—the cap of the cylinder head 2—valve 3—engine block 4—flywheel 5—crankshaft 6—oil pan 7—pulley 8—cylinder 9—timing gearClassification of EngineThe engine can be classified in following ways:By Fuel System 李鹏Gasoline engine and diesel engine are used. In a gasoline engine, the air-fuel mixture is exploded in the engine. A diesel engine uses diesel fuel. It generates high power at low speeds. The fuel efficiency is better than that of a gasoline engine.Unit 2 The Basic Principle of Engine✩ By Cylinder Arrangemen t曾昭昕Most cars have more than one cylinder. Four, six and eight cylinders are common used. In a multi-cylinder engine, the cylinders are usually arranged in one of three ways: in-line, V-type, or flat (Fig.2.2). Today the number of cylinders is growing, the cylinders also can be arranged as W-type.(a) flat (b) V-type (c) in-lineFig.2.2 Cylinder Arrangement✩ By Cooling System 梁松雨Liquid-cooled engines and air-cooled engines are being used. Liquid-cooled engines are the most common in the engine industry.There are also other ways to classify the engines. Despite of these classifications, the structure of the engine is basically the same.Main Components曾润泽The engine consists of several different mechanisms and systems including cylinder block, crankshaft and connecting rod mechanism, valve mechanism, fuel supply system, lubrication system, cooling system, ignition system and starting system.张永德✩ Cylinder BlockThe core of the engine is the cylinder, with the piston moving up and down inside the cylinder.✩ Crankshaft and Connecting Rod MechanismThe crankshaft changes the linear movement of the piston into a rotational movement via a connecting rod. The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.张进✩ Valve MechanismA valve mechanism is a group of components that opens and closes the intake and exhaust valves in the cylinder head at the appropriate time. The main functions of the valve gear are to provide timely admission of the fresh charge into the cylinders and exhaust of spent gases from them.1112汽车专业英语夏磊✩ Fuel Supply SystemThe fuel system supplies fuel to the engine. It also has the functions to regulate the volume of fuel supply. The fuel systems in diesel and gasoline engines are different.于晨雪✩ Lubrication SystemThe lubrication system uses an oil pump to continuously supply engine oil throughout the inside of the engine. This system reduces friction between parts with a film of oil. If the engine is run without oil, the friction can cause poor running, or cause even meltdown. In addition to lubrication, engine oil cools and cleans the engine.滕兆磊✩ Cooling SystemThe cooling system regulates the engine temperature to an optimal level (80℃ to 90℃ at coolant temperature) by circulating the coolant throughout the engine under all operating conditions and during all seasons of the year. The cooling fan cools the coolant in the radiator and water pump circulates the coolant through the cylinder head and the cylinder block.吕庆怡✩ Ignition SystemInternal combustion engines require ignition of the mixture, either by spark ignition (SI) or compression ignition (CI).✩ Starting SystemThe starting system forces the engine to crank with an electric motor, and starts the engine.Text B Engine Operating Principles[zhuangjihui]A four-stroke engine, also known as four-cycle, is an internal combustion engine in which the piston completes four separate strokes ：intake, compression, power and exhaust —during two separate revolutions of the engine’s crankshaft, and one singlethermodynamic cycle.The main parts in four stroke engine are shown in Fig.2.3.Fig.2.3 Main Parts in Four Stroke Engine1—intake valve 2—spark plug 3—exhaust valve 4—combustion chamber 5—piston head13Unit 2 The Basic Principle of Engine[wangxiaolong]As their name implies, four-stroke internal combustion engines have four basic steps that repeat with every two revolutions of the crankshaft:① Intake stroke ② Compression stroke, ③ Power stroke, ④ Exhaust stroke. The four strokes will be illustrated in Fig.2.4.[liyang]They draw in an air-fuel mixture to the cylinders, compress it, ignite and combust it, then discharge it. Repeating these four actions gives gasoline engines their power. The cycle begins at Top Dead Centre (TDC), when the piston is farthest away from the crankshaft. A cycle refers to the full travel of the piston from TDC to Bottom Dead Centre (BDC).[renwenjie]✩ Intake StrokeOn the intake stroke of the piston, the piston descends from (TDC,BDC) to (TDC, BDC), reducing the pressure inside the cylinder. A mixture of fuel and air, or just air in a diesel engine, is forced by atmospheric pressure into the cylinder through the intake port. The intake valve(s) then (open,close).[zhangshuai]✩ Compression StrokeWith both intake and exhaust valves (open,close), the piston returns to the top of the cylinder compressing the fuel-air mixture into the combustion chamber of the cylinder head.[zhantianbao]✩ Power StrokeIt is also named as combustion stroke. While the piston is close to (TDC,BDC), the compressed air –fuel mixture is ignited. The resulting massive pressure from the combustion of the compressed fuel-air mixture forces the piston back down toward (TDC,BDC).[zhangzhikai]✩ Exhaust StrokeDuring the exhaust stroke, the piston once again returns to (TDC,BDC) while the exhaust valve is (open,close). This action evacuates the burnt products of combustion from the cylinder by expelling the spent fuel-air mixture out through the exhaust valve(s)..(1) intake (2) compression (3) power (4) exhaustFig.2.4 Four Stroke Cycle汽车专业英语[heguangbin\youhailong]NEW WORDS AND PHRASESprinciple [ ☐❒♓⏹♦☜☐●] n. 原理，法则n. 种类，类别classification[ ●✌♦♓♐♓♏♓☞☜⏹]n. 布局，构造configuration[ ☜⏹♐♓♈◆❒♏♓☞☜⏹]oxygen [ ♦♓♎✞☜⏹] n. 氧气combustion [ ☜❍♌✈♦♦☞☜⏹] n. 燃烧chamber [ ♦☞♏♓❍♌☜] n. 室，房间component [ ☜❍☐☜◆⏹☜⏹♦] n. 成分，部件，零件force [♐♦] n. 力gasoline [ ♈✌♦☜●♓⏹] n. 汽油diesel [ ♎♓☜●] n. 柴油；柴油机explode [♓♦☐●☜◆♎] n. 爆炸，爆发rotational [❒☜◆♦♏♓☞☜⏹☜●] adj. 旋转的in-line [ ♓⏹●♋♓⏹] adj. (汽缸)直列的flat [♐●✌♦] adj. (汽缸)水平对置cooling system 冷却系liquid-cooled 水冷air-cooled 风冷cylinder block 汽缸体crankshaft [ ❒✌☠☞♐♦] n. 曲柄轴，机轴connecting rod 连杆valve mechanism [ ❍♏☜⏹♓☜❍] 配气机构fuel supply system 燃油供给系lubrication[ ●◆♌❒♓♏♓☞☜⏹] 润滑lubrication system 润滑系ignition system 点火系starting system 起动系linear [ ●♓⏹♓☜] adj. 线性的piston [ ☐♓♦♦☜⏹] n. 活塞intake [ ♓⏹♦♏♓] n. 吸入；进气口，入口exhaust [♓♈♦♦] n. 排气；废气valve [ ✌●] n. 气门，阀门oil pump 机油泵friction [ ♐❒♓☞☜⏹] n. 摩擦(力)14Unit 2 The Basic Principle of Enginepart [☐♦] n. 零件, 部位appropriate [☜☐❒☜◆☐❒♓♓♦] adj. 恰当的，适当的volume[ ●◆❍ ☎U.S.✆ ☜❍] n. 容量，容积a film of oil 一层油膜meltdown [ ❍♏●♦♎♋◆⏹] n. 熔毁optimal [ ☐♦♓❍☜●] adj. 最佳的，最优的coolant [ ◆●☜⏹♦] n. 冷却液，冷冻剂radiator [ ❒♏♓♎♓♏♓♦☜] n. 散热器water pump 抽水机，水泵spark ignition (SI) 火花点火压缩点火compression [ ☜❍☐❒♏☞☎✞✆⏹]ignition (CI)four-stroke 四冲程的(内燃机)power [ ☐♋◆☜] n. 做功illustrate[ ♓●☜♦♦❒♏♓♦] vt. 说明，阐明revolution [ ❒♏☜●◆☞☜⏹] n. 旋转(一周)spark plug 火花塞discharge [♎♓♦♦☞♎✞] vt. 释放；排出Top Dead Centre (TDC) 上止点Bottom Dead Centre (BDC) 下止点descend [♎♓♦♏⏹♎] vi. 下降，降临evacuate [♓✌◆♏♓♦] vi. 散离，释放NOTES TO THE TEXT1. The internal combustion engine is an engine in which the combustion of fuel occurs with oxygen(usually air) in a combustion chamber.内燃机是一种由燃料和氧气(通常是空气)在燃烧室中燃烧而产生动力的发动机。